This invention relates generally to industrial robots with horizontally movable arms and, particularly, to an industrial robot having a horizontal arm which is movable quickly and reliably.
A conventional industrial robot similar to what is disclosed in Japanese Patent Application Kokai No. 58-211,889 is shown in FIG. 1. This industrial robot includes a body 1, an elevation trunk 2, a horizontal upper arm 3, one end of which is operably connected to the upper end of the elevation trunk 2, a shoulder 4 provided on the top of the elevation trunk 2 and composed of an electric motor and a speed reducer to swing the upper arm 3 in a horizontal plane, a horizontal forearm 5 operably connected to the other end of the upper arm 3, and an elbow 6 provided on the other end of the upper arm 3 and composed of an electric motor and a speed reducer to swing the forearm 5.
Further, it includes a hand 7 operably connected to the other end of the forearm 5, a wrist 8 provided at the other end of the forearm 5 and composed of an electric motor and a speed reducer to rotate the hand 7, a first cable 9 extending from the body 1 to the shoulder 4, a second cable 10 extending from the body to the elbow 6, a third cable 11 extending from the body 1 to the wrist 8, and a cable holder 12 for holding the middle portions of the second and third cables 10 and 11.
The hand 7 of the above conventional robot is brought into a desired position as follows. The elevation trunk 2 is moved vertically to position the upper arm 3 at a desired height. The shoulder 4 is then energized via the first cable 9 to swing the upper arm 3 to a desired position. The elbow 6 is then energized via the second cable 10 to swing the forearm 5 to a desired position. The wrist 8 is then energized via the third cable 11 to rotate the hand 7 to a desired position. After the hand 7 has performed a desired operation, the respective shoulder 4, elbow 6, and wrist 8 are energized for the next operation.
However, the above conventional robot has the heavy shoulder 4, elbow 6, and wrist 8 on the respective ends of horizontal arms 3, 5 and the heavy cables 9-11 for energizing these joint devices. Consequently, these joint devices must have large outputs in order to operate these arms with high acceleration or deceleration at high speed. The large weight of these joint devices makes it difficult to move the arms quickly. In addition, the cables 9-11, placed along the outside of arms, are liable to breakdown, resulting in malfunction of the robot. Moreover, since the upper arm 3 and forearm 5 are made integrally, it is difficult to meet particular requirements, such as mounting horizontal arms of different lengths or a hand in different directions.